Add an ID blacklist for Heading Permalink extension

[nicholasbrantley]

Description

It would be nice if there was an option to have a blacklist of HTML IDs that should be considered "already used" when generating the anchor IDs. These would be handled like they were a duplicate heading where the count is appended to it.

This would be an alternative to having to use id_prefix and prepending something to all the IDs, that way they can look normal besides the blacklisted ones.

Example

Have an array for the config:

$config = [
    'heading_permalink' => [
        'id_blacklist' => ['example-id', 'another-example'],
    ],
];

Then if you have headings that generate an ID that matches one in the list:

## Example ID

...

## Another Example

...

## Another Example 

...

...it would generate the IDs as if they were already used:

<h2>Example ID <a id="example-id-1" href="#example-id-1"></h2>

...

<h2>Another Example <a id="another-example-1" href="#another-example-1"></h2>

...

<h2>Another Example <a id="another-example-2" href="#another-example-2"></h2>

...

Did this project help you today? Did it make you happy in any way?

No response